Gear oil compositions, methods of making and using thereof

ABSTRACT

A gear oil composition is provided. The composition comprises a sufficient amount of an isomerized base oil in a base oil matrix comprising at least at least a polyalphaolefin for the gear oil composition to have for the gear oil composition to have an average volume change in a rubber seal between −10 and +10, a change in shore A hardness between −7 and +10 when tested with SRE NBR28 at 100° C., 168 hours per DIN53521 and DIN53505, a viscosity increase of less than 3% per US Steel S-200 oxidation stability test, a precipitation of less than 1% per US Steel S-200 oxidation stability test, and a Timken OK Load of greater than 60 lb. The isomerized base oil has consecutive numbers of carbon atoms and less than 10 wt % naphthenic carbon by n-d-M. In one embodiment, the sufficient amount of isomerized base oil ranges from 20 to 75 wt. % based on the total weight of the gear oil composition.

RELATED APPLICATIONS

NONE

TECHNICAL FIELD

The invention relates generally to compositions suitable for use as lubricants, particularly for use as gear oils.

BACKGROUND

Gear oil is used in industrial applications as well moving equipment such as automobiles, tractors, and the like (collectively referred to as “equipment’). When in use in some applications, the gear oil is present as an oil film between the moving parts, e.g., traction drives.

In a number of patent publications and applications, i.e., US 2006/0289337, US2006/0201851, US2006/0016721, US2006/0016724, US2006/0076267, US2006/020185, US2006/013210, US2005/0241990, US2005/0077208, US2005/0139513, US2005/0139514, US2005/0133409, US2005/0133407, US2005/0261147, US2005/0261146, US2005/0261145, US2004/0159582, U.S. Pat. No. 7,018,525, U.S. Pat. No. 7,083,713, U.S. application Ser. Nos. 11/400570, 11/535165 and 11/613936, which are incorporated herein by reference, a Fischer Tropsch base oil is produced from a process in which the feed is a waxy feed recovered from a Fischer-Tropsch synthesis. The process comprises a complete or partial hydroisomerization dewaxing step, using a dual-functional catalyst or a catalyst that can isomerize paraffins selectively. Hydroisomerization dewaxing is achieved by contacting the waxy feed with a hydroisomerization catalyst in an isomerization zone under hydroisomerizing conditions. The Fischer-Tropsch synthesis products can be obtained by well-known processes such as, for example, the commercial SASOL® Slurry Phase Fischer-Tropsch technology, the commercial SHELL® Middle Distillate Synthesis (SMDS) Process, or by the non-commercial EXXON® Advanced Gas Conversion (AGC-21) process. Details of these processes and others are described in, for example, EP-A-776959, EP-A-668342; U.S. Pat. Nos. 4,943,672, 5,059,299, 5,733,839, and RE39073; and US Published Application No. 2005/0227866, WO-A-9934917, WO-A-9920720 and WO-A-05107935. The Fischer-Tropsch synthesis product usually comprises hydrocarbons having 1 to 100, or even more than 100 carbon atoms, and typically includes paraffins, olefins and oxygenated products. Fischer Tropsch is a viable process to generate clean alternative hydrocarbon products.

There is a need for a gear oil composition containing alternative hydrocarbon products having excellent load carrying capacity, high oxidative stability, and seal compatibility.

SUMMARY OF THE INVENTION

In one aspect, the invention relates to a gear oil composition comprising: a) a base oil containing a synergistic mixture of at least an isomerized base oil having consecutive numbers of carbon atoms and less than 10 wt % naphthenic carbon by n-d-M, and a polyalphaolefin base stock having a kinematic viscosity of 3 to 120 mm²/s at 100° C. and a viscosity index of at least 60; b) 0.001 to 30 wt % at least an additive selected from traction reducers, dispersants, viscosity modifiers, pour point depressants, antifoaming agents, antioxidants, rust inhibitors, metal passivators, extreme pressure agents, friction modifiers, and mixtures thereof, wherein the isomerized base oil is present in a sufficient amount for the gear oil composition to have an average volume change in a rubber seal between −10 and +10, and a change in shore A hardness between −7 and +10 when tested with SRE NBR28 at 100° C., 168 hours per DIN53521 and DIN53505. In one embodiment, the gear oil composition further has a viscosity increase of less than 3% per US Steel S-200 oxidation stability test, a precipitation of less than 1% per US Steel S-200 oxidation stability test, and a Timken OK Load of greater than 60 lb.

In another aspect, the invention relates to a method for improving the oxidative stability and seal compatibility properties of a gear oil composition, the method comprises adding to a base oil matrix comprising a polyalphaolefin from 20 to 75 wt. % (based on the total weight of the gear oil composition) of an isomerized base oil, for the gear oil composition to have an average volume change in a rubber seal between −10 and +10, a change in shore A hardness between −7 and +10 when tested with SRE NBR28 at 100° C., 168 hours per DIN53521 and DIN53505, and a viscosity increase of less than 3% per US Steel S-200 oxidation stability test.

DETAILED DESCRIPTION

The following terms will be used throughout the specification and will have the following meanings unless otherwise indicated.

“Fischer-Tropsch derived” means that the product, fraction, or feed originates from or is produced at some stage by a Fischer-Tropsch process. As used herein, “Fischer-Tropsch base oil” may be used interchangeably with “FT base oil,” “FTBO,” “GTL base oil” (GTL: gas-to-liquid), or “Fischer-Tropsch derived base oil.”

As used herein, “isomerized base oil” refers to a base oil made by isomerization of a waxy feed.

As used herein, a “waxy feed” comprises at least 40 wt % n-paraffins. In one embodiment, the waxy feed comprises greater than 50 wt % n-paraffins. In another embodiment, greater than 75 wt % n-paraffins. In one embodiment, the waxy feed also has very low levels of nitrogen and sulphur, e.g., less than 25 ppm total combined nitrogen and sulfur, or in other embodiments less than 20 ppm. Examples of waxy feeds include slack waxes, deoiled slack waxes, refined foots oils, waxy lubricant raffinates, n-paraffin waxes, NAO waxes, waxes produced in chemical plant processes, deoiled petroleum derived waxes, microcrystalline waxes, Fischer-Tropsch waxes, and mixtures thereof. In one embodiment, the waxy feeds have a pour point of greater than 50° C. In another embodiment, greater than 60° C.

“Kinematic viscosity” is a measurement in mm²/s of the resistance to flow of a fluid under gravity, determined by ASTM D445-06.

“Viscosity index” (VI) is an empirical, unit-less number indicating the effect of temperature change on the kinematic viscosity of the oil. The higher the VI of an oil, the lower its tendency to change viscosity with temperature. Viscosity index is measured according to ASTM D 2270-04.

Cold-cranking simulator apparent viscosity (CCS VIS) is a measurement in millipascal seconds, mPa·s to measure the viscometric properties of lubricating base oils under low temperature and low shear. CCS VIS is determined by ASTM D 5293-04.

The boiling range distribution of base oil, by wt %, is determined by simulated distillation (SIMDIS) according to ASTM D 6352-04, “Boiling Range Distribution of Petroleum Distillates in Boiling Range from 174 to 700° C. by Gas Chromatography.”

“Noack volatility” is defined as the mass of oil, expressed in weight %, which is lost when the oil is heated at 250° C. with a constant flow of air drawn through it for 60 min., measured according to ASTM D5800-05, Procedure B.

Brookfield viscosity is used to determine the internal fluid-friction of a lubricant during cold temperature operation, which can be measured by ASTM D 2983-04.

“Pour point” is a measurement of the temperature at which a sample of base oil will begin to flow under certain carefully controlled conditions, which can be determined as described in ASTM D 5950-02.

“Auto ignition temperature” is the temperature at which a fluid will ignite spontaneously in contact with air, which can be determined according to ASTM 659-78.

“Ln” refers to natural logarithm with base “e.”

“Traction coefficient” is an indicator of intrinsic lubricant properties, expressed as the dimensionless ratio of the friction force F and the normal force N, where friction is the mechanical force which resists movement or hinders movement between sliding or rolling surfaces. Traction coefficient can be measured with an MTM Traction Measurement System from PCS Instruments, Ltd., configured with a polished 19 mm diameter ball (SAE AISI 52100 steel) angled at 220 to a flat 46 mm diameter polished disk (SAE AISI 52100 steel). The steel ball and disk are independently measured at an average rolling speed of 3 meters per second, a slide to roll ratio of 40 percent, and a load of 20 Newtons. The roll ratio is defined as the difference in sliding speed between the ball and disk divided by the mean speed of the ball and disk, i.e. roll ratio=(Speed1−Speed2)/((Speed1+Speed2)−/2).

As used herein, “consecutive numbers of carbon atoms” means that the base oil has a distribution of hydrocarbon molecules over a range of carbon numbers, with every number of carbon numbers in-between. For example, the base oil may have hydrocarbon molecules ranging from C22 to C36 or from C30 to C60 with every carbon number in-between. The hydrocarbon molecules of the base oil differ from each other by consecutive numbers of carbon atoms, as a consequence of the waxy feed also having consecutive numbers of carbon atoms. For example, in the Fischer-Tropsch hydrocarbon synthesis reaction, the source of carbon atoms is CO and the hydrocarbon molecules are built up one carbon atom at a time. Petroleum-derived waxy feeds have consecutive numbers of carbon atoms. In contrast to an oil based on poly-alpha-olefin (“PAO”), the molecules of an isomerized base oil have a more linear structure, comprising a relatively long backbone with short branches. The classic textbook description of a PAO is a star-shaped molecule, and in particular tridecane, which is illustrated as three decane molecules attached at a central point. While a star-shaped molecule is theoretical, nevertheless PAO molecules have fewer and longer branches that the hydrocarbon molecules that make up the isomerized base oil disclosed herein.

“Molecules with cycloparaffinic functionality” mean any molecule that is, or contains as one or more substituents, a monocyclic or a fused multicyclic saturated hydrocarbon group.

“Molecules with monocycloparaffinic functionality” mean any molecule that is a monocyclic saturated hydrocarbon group of three to seven ring carbons or any molecule that is substituted with a single monocyclic saturated hydrocarbon group of three to seven ring carbons.

“Molecules with multicycloparaffinic functionality” mean any molecule that is a fused multicyclic saturated hydrocarbon ring group of two or more fused rings, any molecule that is substituted with one or more fused multicyclic saturated hydrocarbon ring groups of two or more fused rings, or any molecule that is substituted with more than one monocyclic saturated hydrocarbon group of three to seven ring carbons.

Molecules with cycloparaffinic functionality, molecules with monocycloparaffinic functionality, and molecules with multicycloparaffinic functionality are reported as weight percent and are determined by a combination of Field Ionization Mass Spectroscopy (FIMS), HPLC-UV for aromatics, and Proton NMR for olefins, further fully described herein.

Oxidator BN measures the response of a lubricating oil in a simulated application. High values, or long times to adsorb one liter of oxygen, indicate good stability. Oxidator BN can be measured via a Dornte-type oxygen absorption apparatus (R. W. Dornte “Oxidation of White Oils,” Industrial and Engineering Chemistry, Vol. 28, page 26, 1936), under 1 atmosphere of pure oxygen at 340° F., time to absorb 1000 ml of O₂ by 100 g. of oil is reported. In the Oxidator BN test, 0.8 ml of catalyst is used per 100 grams of oil. The catalyst is a mixture of soluble metal-naphthenates simulating the average metal analysis of used crankcase oil. The additive package is 80 millimoles of zinc bispolypropylenephenyldithiophosphate per 100 grams of oil.

Molecular characterizations can be performed by methods known in the art, including Field Ionization Mass Spectroscopy (FIMS) and n-d-M analysis (ASTM D 3238-95 (Re-approved 2005) with normalization). In FIMS, the base oil is characterized as alkanes and molecules with different numbers of unsaturations. The molecules with different numbers of unsaturations may be comprised of cycloparaffins, olefins, and aromatics. If aromatics are present in significant amount, they would be identified as 4-unsaturations. When olefins are present in significant amounts, they would be identified as 1-unsaturations. The total of the 1-unsaturations, 2-unsaturations, 3-unsaturations, 4-unsaturations, 5-unsaturations, and 6-unsaturations from the FIMS analysis, minus the wt % olefins by proton NMR, and minus the wt % aromatics by HPLC-UV is the total weight percent of molecules with cycloparaffinic functionality. If the aromatics content was not measured, it was assumed to be less than 0.1 wt % and not included in the calculation for total weight percent of molecules with cycloparaffinic functionality. The total weight percent of molecules with cycloparaffinic functionality is the sum of the weight percent of molecules with monocycloparaffinic functionality and the weight percent of molecules with multicycloparaffinic functionality.

Molecular weights are determined by ASTM D2503-92(Reapproved 2002). The method uses thermoelectric measurement of vapour pressure (VPO). In circumstances where there is insufficient sample volume, an alternative method of ASTM D2502-04 may be used; and where this has been used it is indicated.

Density is determined by ASTM D4052-96 (Reapproved 2002). The sample is introduced into an oscillating sample tube and the change in oscillating frequency caused by the change in the mass of the tube is used in conjunction with calibration data to determine the density of the sample.

Weight percent olefins can be determined by proton-NMR according to the steps specified herein. In most tests, the olefins are conventional olefins, i.e. a distributed mixture of those olefin types having hydrogens attached to the double bond carbons such as: alpha, vinylidene, cis, trans, and tri-substituted, with a detectable allylic to olefin integral ratio between 1 and 2.5. When this ratio exceeds 3, it indicates a higher percentage of tri or tetra substituted olefins being present, thus other assumptions known in the analytical art can be made to calculate the number of double bonds in the sample. A solution of 5-10% of the sample in deuterochloroform can be prepared, giving a normal proton spectrum of at least 12 ppm spectral width. Tetramethylsilane (TMS) can be used as an internal reference standard. The instrument used to acquire the spectrum and reference the chemical shift has sufficient gain range to acquire a signal without overloading the receiver/ADC, with a minimum signal digitization dynamic range of at least 65,000 when a 30 degree pulse is applied. The intensities of the proton signals in the region of 0.5-1.9 ppm (methyl, methylene and methine groups), 1.9-2.2 ppm (allylic) and between 6.0-4.5 ppm (olefin) are measured. Using the average molecular weight (estimated by vapor pressure osmometry by ASTM D 2503-92[re-approved 2002]) of each distillate range paraffin feed, the following can be calculated: (1) the average molecular formula of the saturated hydrocarbons; (2) the average molecular formula of the olefins; (3) the total integral intensity (i.e. the sum of all the integral intensities); (4) the integral intensity per sample hydrogen (i.e. the total integral intensity divided by the number of hydrogens in the formula; (5) the number of olefin hydrogens (i.e. the olefin integral divided by the integral per hydrogen); (6) the number of double bonds (i.e. the olefin hydrogen multiplied by the hydrogens in the olefin formula divided by 2); and (7) the weight percent olefins (i.e. 100 multiplied by the number of double bonds multiplied by the number of hydrogens in a typical olefin molecule divided by the number of hydrogens in a typical distillate range paraffin feed molecule). This Proton NMR procedure to calculate the olefin content of the sample works best when the olefin content is low, e.g., less than about 15 weight percent.

Weight percent aromatics in one embodiment can be measured by HPLC-UV. In one embodiment, the test is conducted using a Hewlett Packard 1050 Series Quaternary Gradient High Performance Liquid Chromatography (HPLC) system, coupled with a HP 1050 Diode-Array UV-Vis detector interfaced to an HP Chem-station. Identification of the individual aromatic classes in the highly saturated base oil can be made on the basis of the UV spectral pattern and the elution time. The amino column used for this analysis differentiates aromatic molecules largely on the basis of their ring-number (or double-bond number). Thus, the single ring aromatic containing molecules elute first, followed by the polycyclic aromatics in order of increasing double bond number per molecule. For aromatics with similar double bond character, those with only alkyl substitution on the ring elute sooner than those with naphthenic substitution. Unequivocal identification of the various base oil aromatic hydrocarbons from their UV absorbance spectra can be accomplished recognizing that their peak electronic transitions are all red-shifted relative to the pure model compound analogs to a degree dependent on the amount of alkyl and naphthenic substitution on the ring system. Quantification of the eluting aromatic compounds can be made by integrating chromatograms made from wavelengths optimized for each general class of compounds over the appropriate retention time window for that aromatic. Retention time window limits for each aromatic class can be determined by manually evaluating the individual absorbance spectra of eluting compounds at different times and assigning them to the appropriate aromatic class based on their qualitative similarity to model compound absorption spectra.

Weight percent aromatic carbon (“Ca”), weight percent naphthenic carbon (“Cn”) and weight percent paraffinic carbon (“Cp”) in one embodiment can be measured by ASTM D3238-95 (Reapproved 2005) with normalization. ASTM D3238-95 (Reapproved 2005) is the Standard Test Method for Calculation of Carbon Distribution and Structural Group Analysis of Petroleum Oils by the n-d-M Method. This method is for “olefin free” feedstocks, i.e., having an olefin content of 2 wt % or less. The normalization process consists of the following: A) If the Ca value is less than zero, Ca is set to zero, and Cn and Cp are increased proportionally so that the sum is 100%. B) If the Cn value is less than zero, Cn is set to zero, and Ca and Cp are increased proportionally so that the sum is 100%; and C) If both Cn and Ca are less than zero, Cn and Ca are set to zero, and Cp is set to 100%.

HPLC-UV Calibration. In one embodiment, HPLC-UV can be used for identifying classes of aromatic compounds even at very low levels, e.g., multi-ring aromatics typically absorb 10 to 200 times more strongly than single-ring aromatics. Alkyl-substitution affects absorption by 20%. Integration limits for the co-eluting 1-ring and 2-ring aromatics at 272 nm can be made by the perpendicular drop method. Wavelength dependent response factors for each general aromatic class can be first determined by constructing Beer's Law plots from pure model compound mixtures based on the nearest spectral peak absorbances to the substituted aromatic analogs. Weight percent concentrations of aromatics can be calculated by assuming that the average molecular weight for each aromatic class was approximately equal to the average molecular weight for the whole base oil sample.

NMR analysis. In one embodiment, the weight percent of all molecules with at least one aromatic function in the purified mono-aromatic standard can be confirmed via long-duration carbon 13 NMR analysis. The NMR results can be translated from % aromatic carbon to % aromatic molecules (to be consistent with HPLC-UV and D 2007) knowing that 95-99% of the aromatics in highly saturated base oils are single-ring aromatics. In another test to accurately measure low levels of all molecules with at least one aromatic function by NMR, the standard D 5292-99 (Reapproved 2004) method can be modified to give a minimum carbon sensitivity of 500:1 (by ASTM standard practice E 386) with a 15-hour duration run on a 400-500 MHz NMR with a 10-12 mm Nalorac probe. Acorn PC integration software can be used to define the shape of the baseline and consistently integrate.

Extent of branching refers to the number of alkyl branches in hydrocarbons. Branching and branching position can be determined using carbon-13 (¹³C) NMR according to the following nine-step process: 1) Identify the CH branch centers and the CH₃ branch termination points using the DEPT Pulse sequence (Doddrell, D. T.; D. T. Pegg; M. R. Bendall, Journal of Magnetic Resonance 1982, 48, 323ff.). 2) Verify the absence of carbons initiating multiple branches (quaternary carbons) using the APT pulse sequence (Patt, S. L.; J. N. Shoolery, Journal of Magnetic Resonance 1982, 46, 535ff.). 3) Assign the various branch carbon resonances to specific branch positions and lengths using tabulated and calculated values known in the art (Lindeman, L. P., Journal of Qualitative Analytical Chemistry 43, 1971 1245ff; Netzel, D. A., et. al., Fuel, 60, 1981, 307ff). 4) Estimate relative branching density at different carbon positions by comparing the integrated intensity of the specific carbon of the methyl/alkyl group to the intensity of a single carbon (which is equal to total integral/number of carbons per molecule in the mixture). For the 2-methyl branch, where both the terminal and the branch methyl occur at the same resonance position, the intensity is divided by two before estimating the branching density. If the 4-methyl branch fraction is calculated and tabulated, its contribution to the 4+methyls is subtracted to avoid double counting. 5) Calculate the average carbon number. The average carbon number is determined by dividing the molecular weight of the sample by 14 (the formula weight of CH₂). 6) The number of branches per molecule is the sum of the branches found in step 4. 7) The number of alkyl branches per 100 carbon atoms is calculated from the number of branches per molecule (step 6) times 100/average carbon number. 8) Estimate Branching Index (BI) by ¹H NMR Analysis, which is presented as percentage of methyl hydrogen (chemical shift range 0.6-1.05 ppm) among total hydrogen as estimated by NMR in the liquid hydrocarbon composition. 9) Estimate Branching proximity (BP) by ¹³C NMR, which is presented as percentage of recurring methylene carbons—which are four or more carbons away from the end group or a branch (represented by a NMR signal at 29.9 ppm) among total carbons as estimated by NMR in the liquid hydrocarbon composition. The measurements can be performed using any Fourier Transform NMR spectrometer, e.g., one having a magnet of 7.0 T or greater. After verification by Mass Spectrometry, UV or an NMR survey that aromatic carbons are absent, the spectral width for the ¹³C NMR studies can be limited to the saturated carbon region, 0-80 ppm vs. TMS (tetramethylsilane). Solutions of 25-50 wt. % in chloroform-d1 are excited by 30 degrees pulses followed by a 1.3 seconds (sec.) acquisition time. In order to minimize non-uniform intensity data, the broadband proton inverse-gated decoupling is used during a 6 sec. delay prior to the excitation pulse and on during acquisition. Samples are doped with 0.03 to 0.05 M Cr (acac)₃ (tris (acetylacetonato)-chromium (III)) as a relaxation agent to ensure full intensities are observed. The DEPT and APT sequences can be carried out according to literature descriptions with minor deviations described in the Varian or Bruker operating manuals. DEPT is Distortionless Enhancement by Polarization Transfer. The DEPT 45 sequence gives a signal all carbons bonded to protons. DEPT 90 shows CH carbons only. DEPT 135 shows CH and CH₃ up and CH₂ 180 degrees out of phase (down). APT is attached proton test, known in the art. It allows all carbons to be seen, but if CH and CH₃ are up, then quaternaries and CH₂ are down. The branching properties of the sample can be determined by ¹³C NMR using the assumption in the calculations that the entire sample was iso-paraffinic. The unsaturates content may be measured using Field Ionization Mass Spectroscopy (FIMS).

The gear oil composition comprises 0.001 to 30 wt. % of optional additives in a base oil matrix. In one embodiment, the base oil matrix is a blend of two components, an isomerized base oil component A and a base component B, comprising at least a polyalphaolefin base oil, with the amount of the isomerized base oil being sufficient for the gear oil composition to have the desired load carrying capacity, high oxidative stability, and seal compatibility properties.

Component A—Isomerized Base Oil: In one embodiment, component A of the base oil matrix comprises at least an isomerized base oil (or blends of isomerized base oils) which the product itself, its fraction, or feed originates from or is produced at some stage by isomerization of a waxy feed from a Fischer-Tropsch process (“Fischer-Tropsch derived base oils”). In another embodiment, the base oil comprises at least an isomerized base oil made from a substantially paraffinic wax feed (“waxy feed”). In a third embodiment, the isomerized base oil comprises mixtures of products made from a substantially paraffinic wax feed as well as products made from a waxy feed from a Fischer-Tropsch process.

Fischer-Tropsch derived base oils are disclosed in a number of patent publications, including for example U.S. Pat. Nos. 6,080,301, 6,090,989, and 6,165,949, and US Patent Publication No. US2004/0079678A1, US20050133409, US20060289337. The Fischer-Tropsch process is a catalyzed chemical reaction in which carbon monoxide and hydrogen are converted into liquid hydrocarbons of various forms including a light reaction product and a waxy reaction product, with both being substantially paraffinic.

In one embodiment the isomerized base oil has consecutive numbers of carbon atoms and has less than 25 wt % naphthenic carbon by n-d-M with normalization. In another embodiment, the amount of naphthenic carbon is less than 10 wt. %. In yet another embodiment the isomerized base oil made from a waxy feed has a kinematic viscosity at 100° C. between 1.5 and 3.5 mm²/s.

In one embodiment, the isomerized base oil is made by a process in which the hydroisomerization dewaxing is performed at conditions sufficient for the base oil to have: a) a weight percent of all molecules with at least one aromatic functionality less than 0.30; b) a weight percent of all molecules with at least one cycloparaffinic functionality greater than 10; c) a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality greater than 20 and d) a viscosity index greater than 28×Ln (Kinematic viscosity at 100° C.)+80.

In another embodiment, the isomerized base oil is made from a process in which the highly paraffinic wax is hydroisomerized using a shape selective intermediate pore size molecular sieve comprising a noble metal hydrogenation component, and under conditions of 600-750° F. (315-399° C.) In the process, the conditions for hydroisomerization are controlled such that the conversion of the compounds boiling above 700° F. (371° C.) in the wax feed to compounds boiling below 700° F. (371° C.) is maintained between 10 wt % and 50 wt %. A resulting isomerized base oil has a kinematic viscosity of between 1.0 and 3.5 mm²/s at 100° C. and a Noack volatility of less than 50 weight %. The base oil comprises greater than 3 weight % molecules with cycloparaffinic functionality and less than 0.30 weight percent aromatics.

In one embodiment the isomerized base oil has a Noack volatility less than an amount calculated by the following equation: 1000×(Kinematic Viscosity at 100° C.)^(−2.7). In another embodiment, the isomerized base oil has a Noack volatility less than an amount calculated by the following equation: 900×(Kinematic Viscosity at 100° C.)^(−2.8). In a third embodiment, the isomerized base oil has a Kinematic Viscosity at 100° C. of >1.808 mm²/s and a Noack volatility less than an amount calculated by the following equation: 1.286+20 (kv100)^(−1.5)+551.8 e^(−kv100), where kv100 is the kinematic viscosity at 100° C. In a fourth embodiment, the isomerized base oil has a kinematic viscosity at 100° C. of less than 4.0 mm²/s, and a wt % Noack volatility between 0 and 100. In a fifth embodiment, the isomerized base oil has a kinematic viscosity between 1.5 and 4.0 mm²/s and a Noack volatility less than the Noack volatility calculated by the following equation: 160−40 (Kinematic Viscosity at 100° C.).

In one embodiment, the isomerized base oil has a kinematic viscosity at 100° C. in the range of 2.4 and 3.8 mm²/s and a Noack volatility less than an amount defined by the equation: 900×(Kinematic Viscosity at 100° C.)^(−2.8)−15). For kinematic viscosities in the range of 2.4 and 3.8 mm²/s, the equation: 900×(Kinematic Viscosity at 100° C.)^(−2.8)−15) provides a lower Noack volatility than the equation: 160−40 (Kinematic Viscosity at 100° C.)

In one embodiment, the isomerized base oil is made from a process in which the highly paraffinic wax is hydroisomerized under conditions for the base oil to have a kinematic viscosity at 100° C. of 3.6 to 4.2 mm²/s, a viscosity index of greater than 130, a wt % Noack volatility less than 12, a pour point of less than −9° C.

In one embodiment, the isomerized base oil has an aniline point, in degrees F., greater than 200 and less than or equal to an amount defined by the equation: 36×Ln(Kinematic Viscosity at 100° C., in mm²/s)+200.

In one embodiment, the isomerized base oil has an auto-ignition temperature (AIT) greater than the AIT defined by the equation: AIT in ° C.=1.6×(Kinematic Viscosity at 40° C., in mm²/s)+300. In a second embodiment, the base oil as an AIT of greater than 329° C. and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C., in mm²/s)+100.

In one embodiment, the isomerized base oil has a relatively low traction coefficient, specifically, its traction coefficient is less than an amount calculated by the equation: traction coefficient=0.009×Ln (kinematic viscosity in mm²/s)−0.001, wherein the kinematic viscosity in the equation is the kinematic viscosity during the traction coefficient measurement and is between 2 and 50 mm²/s. In one embodiment, the isomerized base oil has a traction coefficient of less than 0.023 (or less than 0.021) when measured at a kinematic viscosity of 15 mm²/s and at a slide to roll ratio of 40%. In another embodiment the isomerized base oil has a traction coefficient of less than 0.017 when measured at a kinematic viscosity of 15 mm²/s and at a slide to roll ratio of 40%. In another embodiment the isomerized base oil has a viscosity index greater than 150 and a traction coefficient less than 0.015 when measured at a kinematic viscosity of 15 mm²/s and at a slide to roll ratio of 40 percent.

In some embodiments, the isomerized base oil having low traction coefficients also displays a higher kinematic viscosity and higher boiling points. In one embodiment, the base oil has a traction coefficient less than 0.015, and a 50 wt % boiling point greater than 565° C. (1050° F.). In another embodiment, the base oil has a traction coefficient less than 0.011 and a 50 wt % boiling point by ASTM D 6352-04 greater than 582° C. (1080° F.).

In some embodiments, the isomerized base oil having low traction coefficients also displays unique branching properties by NMR, including a branching index less than or equal to 23.4, a branching proximity greater than or equal to 22.0, and a Free Carbon Index between 9 and 30. In one embodiment, the base oil has at least 4 wt % naphthenic carbon, in another embodiment, at least 5 wt % naphthenic carbon by n-d-M analysis by ASTM D 3238-95 (Reapproved 2005) with normalization.

In one embodiment, the isomerized base oil is produced in a process wherein the intermediate oil isomerate comprises paraffinic hydrocarbon components, and in which the extent of branching is less than 7 alkyl branches per 100 carbons, and wherein the base oil comprises paraffinic hydrocarbon components in which the extent of branching is less than 8 alkyl branches per 100 carbons and less than 20 wt % of the alkyl branches are at the 2 position. In one embodiment, the FT base oil has a pour point of less than −8° C.; a kinematic viscosity at 100° C. of at least 3.2 mm²/s; and a viscosity index greater than a viscosity index calculated by the equation of =22×Ln (kinematic viscosity at 100° C.)+132.

In one embodiment, the base oil comprises greater than 10 wt. % and less than 70 wt. % total molecules with cycloparaffinic functionality, and a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality greater than 15.

In one embodiment, the isomerized base oil has an average molecular weight between 600 and 1100, and an average degree of branching in the molecules between 6.5 and 10 alkyl branches per 100 carbon atoms. In another embodiment, the isomerized base oil has a kinematic viscosity between about 8 and about 25 mm²/s and an average degree of branching in the molecules between 6.5 and 10 alkyl branches per 100 carbon atoms.

In one embodiment, the isomerized base oil is obtained from a process in which the highly paraffinic wax is hydroisomerized at a hydrogen to feed ratio from 712.4 to 3562 liter H₂/liter oil, for the base oil to have a total weight percent of molecules with cycloparaffinic functionality of greater than 10, and a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality of greater than 15. In another embodiment, the base oil has a viscosity index greater than an amount defined by the equation: 28×Ln (Kinematic viscosity at 100° C.)+95. In a third embodiment, the base oil comprises a weight percent aromatics less than 0.30; a weight percent of molecules with cycloparaffinic functionality greater than 10; a ratio of weight percent of molecules with monocycloparaffinic functionality to weight percent of molecules with multicycloparaffinic functionality greater than 20; and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C.)+110. In a fourth embodiment, the base oil further has a kinematic viscosity at 100° C. greater than 6 mm²/s. In a fifth embodiment, the base oil has a weight percent aromatics less than 0.05 and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C.)+95. In a sixth embodiment, the base oil has a weight percent aromatics less than 0.30, a weight percent molecules with cycloparaffinic functionality greater than the kinematic viscosity at 100° C., in mm²/s, multiplied by three, and a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality greater than 15.

In one embodiment, the isomerized base oil contains between 2 and 10 wt % naphthenic carbon as measured by n-d-M. In one embodiment, the base oil has a kinematic viscosity of 1.5-3.0 mm²/s at 100° C. and 2-3 wt % naphthenic carbon. In another embodiment, a kinematic viscosity of 1.8-3.5 mm²/s at 100° C. and 2.5-4 wt % naphthenic carbon. In a third embodiment, a kinematic viscosity of 3-6 mm²/s at 100° C. and 2.7-5 wt % naphthenic carbon. In a fourth embodiment, a kinematic viscosity of 10-30 mm²/s at 100° C. and between greater than 5.2% and less than 25 wt % naphthenic carbon.

In one embodiment, the isomerized base oil has an average molecular weight greater than 475; a viscosity index greater than 140, and a weight percent olefins less than 10. The base oil improves the air release and low foaming characteristics of the mixture when incorporated into the gear oil composition.

In one embodiment, the isomerized base oil is a white oil as disclosed in U.S. Pat. No. 7,214,307 and US Patent Publication US20060016724. In one embodiment, the isomerized base oil is a white oil having a kinematic viscosity at 100° C. between about 1.5 cSt and 36 mm²/s, a viscosity index greater than an amount calculated by the equation: Viscosity Index=28×Ln (the Kinematic Viscosity at 100° C.)+95, between 5 and less than 18 weight percent molecules with cycloparaffinic functionality, less than 1.2 weight percent molecules with multicycloparaffinic functionality, a pour point less than 0° C. and a Saybolt color of +20 or greater.

Component B—Group IV Polyalphaolefins (“PAOs”): Component B of the base oil matrix is a Group IV base oil or a mixture of different Group IV base oils. Group IV base stocks consist of polyalphaolefins (“PAOs”), offering superior volatility, thermal stability, oxidative stability and pour point characteristics compared to those of the Group II and III oils with less reliance on additives.

PAOs comprise a class of hydrocarbons manufactured by the catalytic oligomerization (polymerization to low-molecular-weight products) of linear α-olefins typically ranging from 1-octene to 1-dodecene, although polymers of lower olefins such as ethylene and propylene can also be used, including copolymers of ethylene with higher olefins. High viscosity PAOs may be conveniently made by the polymerization of an α-olefin in the presence of a polymerization catalyst such as the Friedel-Crafts catalysts including, for example, aluminum trichloride, boron trifluoride or complexes of boron trifluoride with water, alcohols such as ethanol, propanol or butanol, carboxylic acids or esters such as ethyl acetate or ethyl propionate.

In one embodiment, the PAO used is predominantly α-olefin, that is, linear terminal olefin. By predominantly is meant that the PAO contains over about 50 mole percent of α-olefins. In another embodiment, the PAO is a high viscosity PAO, comprising hydrogenated polymers or oligomers of α-olefins. The α-olefins include, but are not limited to, C₂ to about C₃₂ α-olefins, e.g., 1-octene, 1-decene, 1-dodecene and the like. In one example, the PAO is a α-olefins selected from the group of poly-1-octene, poly-1-decene, and poly-1-dodecene.

The PAO products for use in the composition can have a wide range of viscosities, varying from highly mobile fluids of low-viscosity, about 2 mm²/s., at 100° C. to higher molecular weight, viscous materials which have viscosities exceeding 1000 mm²/s (cSt.) at 100° C. The PAO base stock for use in the composition can have a wide range of viscosities, varying from highly mobile fluids of low-viscosity, about 2 mm²/s., at 100° C. to higher molecular weight, viscous materials which have viscosities exceeding 1000 mm²/s (cSt.) at 100° C. In one embodiment, the PAO base stock has a kinematic viscosity ranging from 2 to 100 mm²/s (cSt.) at 100° C.

In one embodiment, the PAO products have a viscosity ranging from 40 to 1250 mm²/s (cSt.) at 40° C. In one embodiment, the PAO has a viscosity of greater than or equal to about 80 mm²/s at 40° C. and less than or equal to about 20 mm²/s at 100° C. In another embodiment, the PAO base stock has a kinematic viscosity @40° C. in the range of 80-110 mm²/s. and a kinematic viscosity @100° C. of 10-16 mm²/s. and a viscosity index of 140-160. In yet another embodiment, the PAO base stock is a blend of different PAOs, one having a viscosity of ranging from 30-60 mm²/s at 40° C. and the other having a viscosity of 300-600 mm²/s at 40° C., for a PAO blend having a viscosity of 100 mm²/s at 40° C.

In one embodiment, the gear oil composition is characterized as having a sufficient amount of isomerized base oil for the composition to have the desired seal compatibility, oxidative stability, and load carrying capability. In one embodiment, this sufficient amount of isomerized base oil (component A) ranges from 20 to 75 wt. % (based on the total weight of the gear oil composition). In a second embodiment, the sufficient amount of isomerized base oil ranges from 30 to 60 wt. %. In a third embodiment, the sufficient amount of isomerized base oil ranges from 40-50 wt. %.

In one embodiment, the gear oil composition comprises a blend of 30 to 40 wt. % (based on the total weight of the gear oil composition) of an isomerized base oil having a kinematic viscosity at 100° C. of 3 to 8 mm²/s., a viscosity index of 145-165, Oxidator BN of 15 to 55 hours; and 60 to 70 wt. % of a poly-α-olefin having a kinematic viscosity of about 40 mm²/s at 100° C. In another embodiment, the gear oil composition comprises a blend of 40 to 80 wt. % (based on the total weight of the gear oil composition) of an isomerized base oil having a kinematic viscosity at 100° C. of 10 to 20 mm²/s., a viscosity index of 155-165, Oxidator BN of 15 to 25 hours; and 35 to 55 wt. % of a poly-α-olefin having a kinematic viscosity of about 40-100 mm²/s at 100° C.

Additional Optional Components: In one embodiment, the gear oil composition comprises 0.01 to 30 wt. % of one or more additives selected from dispersants, viscosity index improvers, pour point depressants, antifoaming agents, antioxidants, rust inhibitors, metal passivators, extreme pressure agents, friction modifiers, etc., in order to satisfy diversified characteristics, e.g., those related to friction, oxidation stability, cleanness and defoaming, etc.

Examples of dispersants include those based on polybutenyl succinic acid imide, polybutenyl succinic acid amide, benzylamine, succinic acid ester, succinic acid ester-amide and a boron derivative thereof. When used, ashless dispersants are typically employed in an amount of 0.05 to 7 wt. %. In one embodiment, the dispersant are selected from the products of reaction of a polyethylene polyamine, e.g. triethylene tetraamine pentaamine, with a hydrocarbon-substituted anhydride made by the reaction of a polyolefin, having a molecular weight of about 700-1400 with an unsaturated polycarboxylic acid or anhydride, e.g. maleic anhydride.

Examples of metallic detergent include those containing a sulfonate, phenate, salicylate of calcium, magnesium, barium or the like. Metallic detergents when used, are typically incorporated in an amount of 0.05 to 5 wt. %.

Examples of antioxidants include but are not limited to amine-based ones, e.g., alkylated diphenylamine, phenyl-α-naphtylamine and alkylated phenyl-x-naphtylamine; phenol-based ones, e.g., 2,6-di-t-butyl phenol, 4,4′-methylenebis-(2,6-di-t-butyl phenol) and isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate; sulfur-based ones, e.g., dilauryl-3,3′-thiodipropionate; and zinc dithiophosphate. When used, antioxidants are incorporated in an amount from 0.05 to 5 wt. %.

Defoaming agents can be optionally incorporated in an amount of 10-100 ppm. Examples of defoaming agents include but are not limited to dimethyl polysiloxane, polyacrylate and a fluorine derivative thereof, and perfluoropolyether. Rust inhibitors can be used in an amount from 0 to 30 wt. %. Examples include a fatty acid, alkenylsuccinic acid half ester, fatty acid soap, alkylsulfonate, polyhydric alcohol/fatty acid ester, fatty acid amine, oxidized paraffin and alkylpolyoxyethylene ether.

Friction modifiers can be incorporated in an amount from 0.05 to 5 wt. %. Examples include but are not limited to organomolybdenum-based compounds, fatty acids, higher alcohols, fatty acid esters, sulfided esters, phosphoric acid ester, acid phosphoric acid esters, acid phosphorus acid esters and amine salt of phosphoric acid ester.

Small amounts of traction reducers, e.g., from 0.5 to 10 wt. %, can be incorporated in the gear oil composition. Examples of traction reducers include ExxonMobil's Norpar™ fluids (comprising normal paraffins), Isopar™ fluids (comprising isoparaffins), Exxsol™ fluids (comprising dearomatized hydrocarbon fluids), Varsol™ fluids (comprising aliphatic hydrocarbon fluids), and mixtures thereof.

Anti-wear and/or extreme pressure agents can be incorporated in an amount from 0.1 to 10 wt. %. Examples of anti-wear and/or extreme pressure agents include metal-free sulfur containing species including sulfurized olefins, dialkyl polysulfides, diarylpolysulfides, sulfurized fats and oils, sulfurized fatty acid esters, trithiones, sulfurized oligomers of C2-C8 monoolefins, thiophosphoric acid compounds, sulfurized terpenes, thiocarbamate compounds, thiocarbonate compounds, sulfoxides, thiol sulfinates, and the like. Other examples include metal-free phosphorus—containing antiwear and/or extreme pressure additives such as esters of phosphorus acids, amine salts of phosphorus acids and phosphorus acid-esters, and partial and total thio analogs of the foregoing. In one embodiment, the composition comprises an acid phosphate as an anti-wear agent, with the agent having the formula R₁O(R₂O)P(O)OH, where R₁ is hydrogen or hydrocarbyl and R₂ is hydrocarbyl.

Pour point depressant can be incorporated in an amount ranging from 0.05 to 10 wt. %. Examples include but are not limited to ethylene/vinyl acetate copolymer, condensate of chlorinated paraffin and naphthalene, condensate of chlorinated paraffin and phenol, polymethacrylate, polyalkyl styrene, chlorinated wax-naphthalene condensate, vinyl acetate-fumarate ester copolymer, and the like.

In one embodiment, the composition further comprises at least one of a polyoxyalkylene glycol, polyoxyalkylene glycol ether, and an ester as a solubilizing agent in an amount from 10 to 25 wt. %. Examples include esters of a dibasic acid (e.g., phthalic, succinic, alkylsuccinic, alkenylsuccinic, maleic, azelaic, suberic, sebacic, fumaric or adipic acid, or linolic acid dimmer) and alcohol (e.g., butyl, hexyl, 2-ethylhexyl, dodecyl alcohol, ethylene glycol, diethylene glycol monoether or propylene glycol); and esters of a monocarboxylic acid of 5 to 18 carbon atoms and polyol (e.g., neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol or tripentaerythritol); polyoxyalkylene glycol ester; and phosphate ester.

In one embodiment, the composition further comprises at least a metal passivator, and sometimes specifically a copper passivator. Examples include thiazoles, triazoles, and thiadizoles. Specific examples of the thiazoles and thiadiazoles include 2-mercapto-1,3,4-thiadiazole, 2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazoles, 2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazoles, 2,5-bis-(hydrocarbylthio)-1,3,4-thiadiazoles, and 2,5-bis-(hydrocarbyldithio)-1,3,4-thiadiazoles. Other suitable inhibitors of copper corrosion include imidazolines, described above, and the like.

In one embodiment, the composition further comprises at least a viscosity modifier in an amount of 0.50 to 10 wt. %. Examples of viscosity modifiers include but are not limited to the group of polymethacrylate type polymers, ethylene-propylene copolymers, styrene-isoprene copolymers, hydrated styrene-isoprene copolymers, polyisobutylene, and mixtures thereof. In one embodiment, the viscosity modifier is a blend of a polymethacryalte having a weight average molecular weight of 25,000 to 150,000 and a shear stability index less than 5 and a polymethacryate having a weight average molecular weight of 500,000 to 1,000,000 and a shear stability index of 25 to 60.

In one embodiment, the gear oil composition optionally comprises a sufficient amount of pour point depressant to cause the pour point of the hydraulic fluid to be at least 3° C. below the pour point of a blend that does not have the pour point depressant. Pour point depressants are known in the art and include, but are not limited to esters of maleic anhydride-styrene copolymers, polymethacrylates, polyacrylates, polyacrylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids, ethylene-vinyl acetate copolymers, alkyl phenol formaldehyde condensation resins, alkyl vinyl ethers, olefin copolymers, and mixtures thereof.

Properties: In one embodiment, the gear oil composition is characterized as being very stable for use with a wide range of temperatures with a viscosity index (VI) of at least 140 (with less than 0.5 wt. % or even no VI improver). In another embodiment, the gear oil composition has a VI of at least 150. In a third embodiment, a VI of at least 160.

A typical test for oxidation stability is US Steel S-200, which is used to measure the ability of gear lubricants to resist oxidation and the formation of deposits when subjected to high operating temperatures. At the end of the test period, the viscosity is checked for change (maximum of five percent increase), the test utensils are inspected for sludge or residue and the lubricant color is checked for evidence of change (darkening). In one embodiment, the gear oil is characterized as having a high oxidation stability when tested per US Steel S-200, with a viscosity increase in one embodiment of less than 3%. In a second embodiment, a viscosity increase of less than 2%. In a third embodiment, of less than 1%. The amount of precipitation under this test is less than 1% in one embodiment, less than 0.05% in a second embodiment, and less than 0.03% in a third embodiment.

In one embodiment, the gear oil composition is characterized as having a Timken OK Load of greater than 60 lb. In a second embodiment, a Timken OK Load of greater than 70 lb. In a third embodiment, greater than 90 lb.

In one embodiment, the gear oil composition is characterized as resulting in an average volume change (swell increase) in a rubber seal between −10 and +10, and a change in shore A hardness between −7 and +10 when tested with SRE NBR28 at 100° C., 168 hours (per DIN53521 and DIN53505). In a second embodiment, the average volume change is between −5 and +5, and a change in shore A hardness between −5 and +5 when tested per DIN53521 and DIN53505.

In one embodiment, the gear oil composition is characterized as having low foaming tendency and excellent air release properties. The foaming tendency of the can be measured using the ASTM D892-E2007 foam test. In one embodiment, the gear oil composition shows a sequence II foam tendency foam height of less than 75 mL. In yet another embodiment, the gear oil composition shows a sequence II foam height of less than 40 mL. In a third embodiment, a sequence II foam height of less than 30 mL. In a fifth embodiment, the sequence II foam height is less than 20 mL. In a sixth embodiment, none can be measured (0 mL).

Air release properties can be measured using the ASTM D 3427 (2006) method for gas bubble separation time of petroleum oil to measure the ability of a fluid to separate entrained gas. In one embodiment, the gear oil composition has an air release time at 50° C. of less than 10 minutes. In a second embodiment, an air release time of less than 8 minutes. In a third embodiment, less than 7 minutes.

Method for Making: Additives used in formulating the gear oil composition can be blended into base oil blends individually or in various sub-combinations. In one embodiment, all of the components are blended concurrently using an additive concentrate (i.e., additives plus a diluent, such as a hydrocarbon solvent). The use of an additive concentrate takes advantage of the mutual compatibility afforded by the combination of ingredients when in the form of an additive concentrate.

In another embodiment, the composition is prepared by mixing the base oil and the additive(s) at an appropriate temperature, e.g., 60° C., until homogeneous.

Applications: The composition is useful in any system that include elements or parts containing gears of any kind and rolling element bearings. In one embodiment, the composition is used as a gear oil for lubricating industrial gears, e.g., spur and bevel, helical and spiral bevel, hypoid, worm, and the like. In another embodiment, the composition is used in automotive/mobile equipment applications and parts, including aircraft propulsion systems, aircraft transmissions, wind turbine gears, automotive drive trains, transmissions, transfer cases, and differentials in automobiles, trucks, and other machinery. In yet another embodiment, the composition is used in wind turbines, plastic extruder gear boxes, and highly loaded gearboxes used in electricity generating systems, or paper, steel, oil, textile, lumber, cement industries, and the like.

EXAMPLES

The examples are given as non-limitative illustrations of aspects of the invention. Properties of the isomerized base oils used in the examples are shown in Table 3.

Examples 1-2

Two gear oil compositions were formulated according to the amounts in Table 1 and tested for seal compatibility. Test Methods DIN 53521 and DIN 53505 were used for SRE NBR-28 nitrile butadiene rubber and 75 FPM 585 fluoroelastomer. The components in the examples are as follows:

FTBO-L (WOW9898) is an isomerized base oil from Chevron Corporation of San Ramon, Calif. The properties of FTBO-L are shown in Table 5.

PAO-4 and PAO-40 are polyalpha olefin (“PAO”) base oils having viscosities of 4 cSt @ 100° C. and 40 cSt @ 100° C., respectively.

Additive 1 (Priolube 3970) is a hindered ester additive.

Additive 2 (Lubrizol 5058) is a gear oil additive package from Lubrizol.

Additive 3 (TX 4238) is a commercially available additive package for gear oil.

As shown in Table 1, the gear oil example comprising at least an isomerized based oil shows a smaller decrease in the mechanical resistance of nitrile and fluoropolymer rubbers (change in max elongation and tensile strength at break), less swelling (volume increase) and less weakening (decrease in hardness) of the fluoropolymer rubber.

TABLE 1 Components Example 1 Example 2 PAO 4 CST 34.00 PAO 40 CST 58.48 58.48 FTBO L 34.00 Additive 1 (PRIOLUBE 3970) 5.00 5.00 Additive 2 (LUBRIZOL 5058) 2.50 2.50 Additive 3 (1TX 4238) 0.02 0.02 Total 100.00 100.00 Test Results Kin. Visc. 40° C., mm²/s 95.1 88.1 Kin. Visc. 100° C., mm²/s 14.29 13.84 VI 155 161 Seal compatibility SRE-NBR 28 DIN 53521 100° C., 168 Relative volume change, % DIN 3.3 3.3 53505 Change in shore A hardness, % 0 −1 Loss of tensile strength, % −15 −14.4 Decrease in elongation at −28.7 −27.1 breakage, % Seal compatibility 75 FKM 585 Static test (130° C., 168 h) Change in Hardness Shore A, % −2 −1 Relative volume change, % 0.7 0.7 Change in tensile strength, % 6.1 4.5 Change in elongation at −13.6 −9.8 breakage, % Storage at room temperature week 1 Bright and Clear week 2 Bright and Clear week 3 Bright and Clear week 4 Bright and Clear

Examples 3-6

In these examples, gear oil lubricants meeting ISO 150 viscosity grade were formulated according to amounts in Table 2 to compare embodiments of the invention with gear oil composition containing POA base oils only, e.g., Timken OK load, oxidative stability, air release properties, demulsibility, compatibility with various seals, rust and corrosion protection. The components used in the examples are as follows:

PAO-6 and PAO-100 are polyalpha olefin (“PAO”) base oils having viscosities of 6 cSt @ 100° C. and 100 cSt @ 100° C., respectively.

HFTBO (PGQ2249) is an isomerized base oil from Chevron Corporation of San Ramon, Calif.

Additive 4 (Esterex A51) is an adipate ester solubility additive.

Additive 5 (Priolube 3970) is a hindered ester additive.

Additive 6 (Lubrizol 5058) is a gear oil additive package from Lubrizol.

Additive 7 (Infineum G-361) is another gear oil additive package, from Infineum International Ltd.

Additive 8 is a commercially available foam inhibitor additive.

TABLE 2 Comp. Comp. Components Example 3 Example 4 Example 5 Example 6 HFTBO (PGQ2249) 74.99 — — 45.91 PAO 6 — 50.44 42.2 — PAO 100 17.51 42.06 41.30 31.59 Additive 4 (Esterex A51) — — 15.00 — Additive 5 (Priolube 3970) 5.00 5.00 — 20.00 Additive 6 (Lubrizol 5058) 2.50 2.50 — 2.50 Additive 7 (Infineum G-361) — — 1.50 — Total, % 100 100 100 100 Additive 8 0.005 0.005 0.005 0.005 Tests Method Visc, Kin, at 40 C., cSt D 445-06 142 143.2 134.7 148 Visc, Kin, at 100 C., cSt D 445-06 19.99 19.73 19.02 20.93 Viscosity Index (min) D 2270-04 164 158 160 166 API Gravity — — — 32.1 Cu Strip, 3 Hr @ 100 C. (max) D130 (E2005) 1a 1b 1b 1a Pour Point; C. (max) D 5950-02 −13 −52 −51 −26 Appearance (max) 2 2 2 Timken OK Load, lb D 2782 >100, 85 95 95 65 (E2006) FZG, Pass Stage 12 12 est. 12 est. 12 12 Rust D 665-06 A-Distilled water — — — — B-Synthetic sea water Pass Pass Pass — Oxidation, 121 C., 312 hr, U.S. Steel 10 li/hr air Vis increase (%), max S-200 2.1 2.4 1.84 0.53 Precipitation no. after test 0.10% <1 <0.02 <0.01 0.025 Demulsibility, for 90 ml water Water in Oil (%), max 0 0.05 0 0 Total free water (ml), min 83 87 86 80 Emulsion (ml), max 1 1 0.05 1 Thermal Stability D 2070 (Cincinnati Lamb) (R 2006) Visc. Change, 40/100 C. — 1.6 — — — Sludge, ml/100 ml — none — — — Cu Rod Color (Cin.Mach.) — 2.5 — — — Steel Rod Color — 1 — — — (Cin.Mach.) Copper Weight Loss, mg — 1.70 — — — Steel Weight Loss, mg — 0.8 — — — Copper Weight Deposit, — 0.9 — — — mg Steel Weight Deposit, mg — 0.1 — — — Foam Tendency/Stability D892 (E2007) Sequence I, ml — 30/20 5/0 0/0 — Sequence II, ml 75/0 0/0 130/0  0/0 — Sequence III, ml — 0/0 70/0  0/0 — Four Ball Wear, 54 C., 1800 rpm, 20 kg, 1 hr Scar diameter, mm, max — 0.356 0.31 0.25 — Four Ball Wear, 75 C., D4172 (E2006) 1200 rpm, 40 kg, 1 hr Scar diameter, mm, max — — 0.43 0.40 — Air Release, min D3427-06 6.55/7.17 8.62 8.5 — Four Ball EP D2783-03 Weld Load, kg — 315, 315 315 250 250 Last Non-seizure Load, kg — 63, 100 160 100 126 Load Wear Index,. Kg — 36.43, 65.5 46.1 54.01 48.1 Compatibility with Seals (ISO 1817) Silicone Average elongation — — no result — — change Volume change, % — 1.75 no result — — Shore A Hardness change, — −3.4 no result — — pts Viton Average elongation −0.22 — — change Volume change, % — 0.34 −0.8 — — Shore A Hardness change, — −1.9 0.87 — — pts Acrylate Average elongation — — change Volume change, % — −0.29 1.4 — — Shore A Hardness change, — −5.4 −0.59 — — pts SRE NBR1 — — −0.12 — — Average elongation — — −17.3 — — change Volume change, % −5/+10 −1.6 0.59 — — Shore A Hardness change, −7/+10 3.32 1.4 — — pts Acid Number — 0.80 0.71 0.51 —

As shown in the above table, gear oil compositions containing a mixture of isomerized base oils and PAO result in better lubrication, better load carrying capacity as shown by Timken OK Load, better oxidative property (as suggested by less increase in viscosity as shown by S-200 US Steel test), better load carrying capability as shown by Four Ball EP test, higher weld load, higher LW Index and no seizure load, better air release properties, excellent demulsibility, excellent compatibility with most common seals, and good rust and corrosion protection.

TABLE 3 Properties FTBO-L HFTBO Chevron Sample ID WOW9898 PGQ2249 Kinematic Viscosity @40° C., mm²/s — 91.64 Kinematic Viscosity @100° C., mm²/s 4.039 13.99 Viscosity Index 150 157 Cold Crank Vis. @−40° C., mPa · s 2,450 — Cold Crank Vis. @−35° C., mPa · s 1,335 — Cold Crank Vis. @ −30° C., mPa · s — — Cold Crank Vis. @ −25° C., mPa · s — — Pour Point, ° C. −25 −8 Aniline Point, ° F. — 288.9 n-d-m ((ASTM D3238-95 Reapproved — — 2005) normalization to 100% total wt % carbon) Molecular Weight, gm/mol (VPO) 416 737 Density, gm/ml 0.8116 0.8009 Refractive Index 1.4536 1.4461 Paraffinic Carbon, % — — Naphthenic Carbon, % — — Aromatic Carbon, % — — Traction Coefficient @ 15 cSt 0.0241 — Oxidator BN, hrs 50.43 18.89 Noack Volatility wt. % 13.01 — COC Flash Point, ° C. — — SIMDIST TBP (WT %), F (ASTM D- 6352-04) TBP @0.5 418 947 TBP @5 723 963 TBP @10 741 972 TBP @20 763 990 TBP @30 780 1006 TBP @40 796 1025 TBP @50 812 1045 TBP @60 829 1066 TBP @70 847 1090 TBP @80 867 1122 TBP @90 887 1168 TBP @95 899 1203 TBP @99.5 921 1273 FIMS by Probe sample introduction Alkanes 78.9 58.5 1-Unsaturation 20.3 40.2 2-Unsaturation 0.8 0.8 3-Unsaturation 0 0 4-Unsaturation 0 0 5-Unsaturation 0 0 6-Unsaturation 0 0 NMR Analysis: Branching Index 26.18 21.08 Branching Proximity 19.02 24.01 Alkyl Branches per Molecule 2.85 4.39 Methyl Branches per Molecule 2.36 3.43 FCI 5.65 12.59 FCI/END Methyl Ratio 4.59 5.02 Alkyl Branches per 100 Carbons 9.58 8.38 Methyl Branches per 100 Carbons 7.94 6.55 % Branches at 2 position 10.80 5.63 % Branches at 3 position 9.11 7.04 % Branches at 2 + 3 positions 19.91 12.68 Percent Branches at 5+positions 50.57 48.59 % Olefins by Proton NMR 0.00 3.17

For the purpose of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained and/or the precision of an instrument for measuring the value, thus including the standard deviation of error for the device or method being employed to determine the value. The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternative are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.” The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” Furthermore, all ranges disclosed herein are inclusive of the endpoints and are independently combinable. In general, unless otherwise indicated, singular elements may be in the plural and vice versa with no loss of generality. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.

It is contemplated that any aspect of the invention discussed in the context of one embodiment of the invention may be implemented or applied with respect to any other embodiment of the invention. Likewise, any composition of the invention may be the result or may be used in any method or process of the invention. This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. All citations referred herein are expressly incorporated herein by reference. 

1. A gear oil composition, comprising: a) a base oil comprising a mixture of at least a polyalphaolefin (PAO) base stock and at least an isomerized base oil having consecutive numbers of carbon atoms, less than 0.05 wt. % aromatics, a wt % total molecules with cycloparaffinic functionality greater than 25 and a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality greater than 10; b) 0.001 to 30 wt % at least an additive selected from traction reducers, dispersants, viscosity modifiers, pour point depressants, antifoaming agents, antioxidants, rust inhibitors, metal passivators, extreme pressure agents, friction modifiers, and mixtures thereof; wherein the isomerized base oil base stock is present in a sufficient amount for the gear oil composition to have an average volume change in a rubber seal between −10 and +10, and a change in shore A hardness between −7 and +10 when tested with SRE NBR28 at 100° C., 168 hours per DIN53521 and DIN53505.
 2. The gear oil composition of claim 1, wherein the isomerized base oil base stock is present in a sufficient amount for the gear oil composition to have an average volume change in a rubber seal between −5 and +5, and a change in shore A hardness between −5 and +5 when tested with SRE NBR28 at 100° C., 168 hours per DIN53521 and DIN53505.
 3. The gear oil composition of claim 2, wherein the isomerized base oil base stock is present in an amount of 30 to 40 wt. % based on the total weight of the gear oil composition.
 4. The gear oil composition of claim 3, wherein the isomerized base oil has a kinematic viscosity at 100° C. of 3 to 8 mm²/s., a viscosity index of 145-165, Oxidator BN of 15 to 55 hours; and wherein the polyalphaolefin base stock has a kinematic viscosity of about 40 mm²/s at 100° C.
 5. The gear oil composition of claim 1, wherein the composition has a viscosity increase of less than 3% per US Steel S-200 oxidation stability test.
 6. The gear oil composition of claim 5, wherein the composition has a viscosity increase of less than 2% per US Steel S-200 oxidation stability test
 7. The gear oil composition of claim 6, wherein the composition has a viscosity increase of less than 1% when tested per US Steel S-200 oxidation stability test
 8. The gear oil composition of claim 1, wherein the composition has a precipitation of less than 1% per US Steel S-200 oxidation stability test.
 9. The gear oil composition of claim 9, wherein the composition has a precipitation of less than 0.05% per US Steel S-200 oxidation stability test.
 10. The gear oil composition of claim 9, wherein the composition has a precipitation of less than 0.03% per US Steel S-200 oxidation stability test.
 11. The gear oil composition of claim 1, wherein the composition has a Timken OK Load of greater than 60 lb.
 12. The gear oil composition of claim 1, wherein the composition has a Timken OK Load of greater than 70 lb.
 13. The gear oil composition of claim 1, wherein the composition has a viscosity increase of less than 3% per US Steel S-200 oxidation stability test, a precipitation of less than 1% per US Steel S-200 oxidation stability test, and a Timken OK Load of greater than 60 lb.
 14. The gear oil composition of claim 13, wherein the isomerized base oil is present in an amount of 40 to 80 wt. % based on the total weight of the gear oil composition.
 15. The gear oil composition of claim 13, wherein the isomerized base oil Has a kinematic viscosity at 100° C. of 10 to 20 mm²/s., a viscosity index of 155-165, Oxidator BN of 15 to 25 hours; and wherein polyalphaolefin base stock has a kinematic viscosity of about 40-100 mm²/s at 100° C.
 16. The composition of claim 1, wherein the isomerized base oil has a total weight percent of molecules with cycloparaffinic functionality of greater than 10, and a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality of greater than
 15. 17. The composition of claim 1, wherein the isomerized base oil is made from a process in which the highly paraffinic wax is hydroisomerized using a shape selective intermediate pore size molecular sieve comprising a noble metal hydrogenation component, and under conditions of about 600° F. to 750° F. and wherein the isomerized base oil has a Noack volatility of less than 50 weight %.
 18. The composition of claim 1, wherein the isomerized base oil has a Noack volatility less than an amount calculated by: 1.286+20 (kv100)^(−1.5)+551.8 e^(−kv100), where kv100 is the kinematic viscosity at 100° C.
 19. The composition of claim 1, wherein the isomerized base oil comprises greater than 3 weight % molecules with cycloparaffinic functionality and less than 0.30 weight percent aromatics.
 20. The composition of claim 1, wherein the isomerized base oil comprises greater than 10 wt. % and less than 70 wt. % total molecules with cycloparaffinic functionality
 21. A method for improving the oxidative stability and seal compatibility properties of a gear oil composition, the method comprises adding a sufficient amount of at least an isomerized base oil to a base oil matrix comprising at least a polyalphaolefin, for the gear oil composition to have an average volume change in a rubber seal between −10 and +10, a change in shore A hardness between −7 and +10 when tested with SRE NBR28 at 100° C., 168 hours per DIN53521 and DIN53505, and a viscosity increase of less than 3% per US Steel S-200 oxidation stability test.
 22. The method of claim 21, wherein the isomerized base oil is present in an amount from 20 to 75 wt. % based on the total weight of the gear oil composition. 